Method and device for the bi-directional transmission of electronic data in a television data cable network

ABSTRACT

The invention relates to a method and an apparatus for bidirectional transmission of electronic data in a television data cable network having segments which each comprise two or more user interfaces, with each of the segments being connected via a cable connection to a feed point in the television data cable network. In the method, electronic downlink remote data is transmitted in a downlink radio-frequency band in an upper cut-off area of a transmission bandwidth of the cable connection, and electronic uplink remote data is transmitted in an uplink radio-frequency band in the upper cut-off area of the transmission bandwidth of the cable connection.

The invention relates to the field of bidirectional transmission ofelectronic data in a television data network based on cables.

Cable networks based on coaxial cables have been upgraded with the aimof transporting television channels to end users and of distributingdata signals within this network such that the maximum number ofcustomers are reached. This relates to unidirectional distribution whosefundamental concept (an analog network) does not offer the capability totransport digital data bidirectionally. This bidirectional transport isrequired in order to make it possible to offer interactive services,such as the Internet. FIG. 1 shows a schematic illustration of thenetwork levels in a conventional cable network. The cable network has alargely homogeneous structure. When planning a network for puretelevision distribution, factors such as the attenuation of the signalsand interference in the coaxial cable are important. As is shown in FIG.1, a broadband cable amplifier point 1 (BKVrSt) is followed by ahigher-level broadband cable amplifier point 2 (ÜBKVrSt). The broadbandcable amplifier point 1 and the higher-level broadband cable amplifierpoint 2 are part of a regional distribution network for supplyingtelevision programs. The local distribution network is followed by aconnection network in which a user-end broadband cable amplifier point 3(BBKVrSt) is arranged. The television data is then distributed in alocal distribution network via A, B and C distributors (A, B and C-Vr).A lines are main lines which originate from a central network node inthe cable network. B lines are lines which branch off from A lines andcarry out a first subdistribution stage. C lines are once again branchesof the B lines, via which line branching of the network is carried out.

The television data is fed via a handover point (ÜP) into a furthernetwork level, in which it is then distributed to the users. Even inrelatively old networks, there are frequently glass-fiber connectionsfor the distribution of television signals between the higher-leverbroadband cable amplifier point 2 and the broadband cable amplifierpoint 3. The amplifier points are arranged downstream from the broadbandcable amplifier point 3, at a maximum distance of 300 m.

Cable network operators are increasingly attempting to extend theirrange of services. This relates to services such as pay-TV, Video onDemand, “high-speed” Internet via the cable network and telephony. Inorder to make it possible to offer Internet data via the cable networks,the cable network must have a return-channel capability, which meansthat data must also be passed back in the opposite direction to thetelevision signals. In this case, approximately 70% of the totalinvestment costs for the technical conversion of the cable network areincurred in the area of the local distribution network and in thedownstream further network level. The magnitude of the investment costsis dependent on how the upgrading of the networks is planned.

With regard to the upgrading of the cable networks, a distinction mustbe drawn between subject areas which are often combined under the commondenominator of upgrading: (i) upgrading to 862 MHz and (ii)return-channel capability. Upgrading to 862 MHz means extending thefrequencies from the conventional 450 MHz to 862 MHz in the cablenetwork, thus providing more capacity in the networks for the services.In conjunction with Internet services, which require a channel for thedownlink datastream (“Downstream”), there is often a deficit of freechannels in the conventional 450 MHz networks. Upgrading to 862 MHz isfrequently carried out in order to make it possible to offer a broaderrange of digital television programs. The configuration of thereturn-channel capability is a type of upgrading of the cable networkswhich allows data to be transported in the reverse direction, and thusin the opposite direction to the conventional television channels. Thismakes it possible, for example, to provide Internet services.

Currently, the upgrading of the cable networks requires relatively largeamounts of investment since use is made of a so-called “Hybrid FiberCoax” (HFC) structure, by means of which the use of glass-fiber andcoaxial cables is combined in one network. In this case, glass-fibercables are replacing the coaxial cables in the area of the localdistribution network. The glass-fiber cables must first of all be laidfor this purpose. FIG. 2 shows the principle of a cable network that hasbeen upgraded using HFC technology. The coaxial cables (Coax) normallyused in the cable network are combined with glass-fiber cables (opticalwaveguides). The use of glass-fiber cables in cable networks differsfrom the use of glass-fiber cables in telecommunications networks.Telecommunications networks transport information independently of thecontent of this data. Irrespective of whether this relates to Internetdata or MPEG image data—transportation in a glass-fiber network is thesame. This results in a high degree of standardization in the network.Television signals are passed on in a transparent form via theglass-fiber cables (in analog or digital form) via the glass fibers inthe HFC network. These signals are transported in glass fibers to afiber node. If it is also intended to offer Internet services, each noderequires two glass-fiber connections; one for the downlink datastreamand one for the return-channel. Since specific information, such as thechannel allocation in the cable network, is already included in thesignal, this does not relate to conventional data standards, as is thecase in the Internet or in WAN networks. The signal is converted fromthe glass-fiber network to the coaxial cable network in the fiber nodes.In this case, the signal is no longer processed since it is already in amodulated form in the glass fiber. The expression a hub is also oftenused at this point, although this has a different function in a purelydigital network.

During the conversion to copper (coaxial cable), the frequency rangefrom 5-65 MHz or 5-45 MHz is used for the return-channel, depending onthe network, and frequencies above 303 MHz are used for the downlinkdata connection. A CMTS (“Cable Modem Termination System”) which is usedin this case has, in particular, the task of assigning the frequenciesfor the downlink datastream and the uplink datastream. In addition, CMTSprovides the link to the wide area network and/or to the Internetservice provider. Here, the signals are converted to atelecommunications standard, for transmission to the wide area network.The connection from the CMTS to a data network is provided by aconventional standard (STM, ATM, 100BaseT, etc.). The downlinkdatastream (downstream) for Internet use is transported in a freetelevision channel to the customer modems.

FIG. 3 shows, schematically, the use of the frequency band for atelevision data cable network as it was originally used (upperillustration in FIG. 3) and using HFC technology (lower illustration inFIG. 3), for comparison. For HFC technology, the return-channel 30 isoperated in the frequency range from 5-65 MHz or 5-45 MHz. Owing to thehigh susceptibility to interference, the modulation method that is usedis QPSK (QPSK—“Quadrature Phase Shift Keying”) up to a maximum of QAM 16(QAM—“Quadrature Amplitude Modulation”) so that a capacity of 3 to 10Mbit/s is available in the return-channel. The CMTS can serve a numberof return-channels at the same time. This results in a concentration ofreturn-channel data at the CMTS level.

Conventional cable networks have a channel allocation with a bandwidthof 8 MHz per channel, as standard. One analog program or 5-6 digitalprograms can be accommodated in one 8 MHz channel. If a channel is leftfree, that is to say it is not used by a television program, then up to52 Mbit/s of modulated data can be transmitted in the downlink. Thischaracteristic is used in order to supply the Internet data to thecustomer in the downlink direction (downstream) via the glass fibersand, later, via the coaxial cable. The assignment of the downlinkdatastream channel to a cable modem via which the customer is connectedto the cable network, as well as the allocation to the cable modem onwhich frequencies from the uplink datastream can be sent, is a functionof the CMTS.

The object of the invention is to provide an improved method andimproved apparatus for bidirectional transmission of electronic data ina television data cable network, which allow implementation, which canbe carried out with less complexity and thus more cost-effectively, ofbidirectional transmission of electronic data for extended mediaservices with a wider bandwidth in the television data cable network.

According to the invention, the object is achieved by a method asclaimed in the independent claim 1, and by an apparatus as claimed inthe independent claim 8.

The invention comprises the idea of forming a return-channel capabilityin a television data cable network by the formation of a backbone in anupper cut-off area of a transmission bandwidth of the cable connectionsof the television data cable network. Both a downlink datastream(downstream) and an uplink datastream (upstream) are provided via thebackbone. The data which has been fed in via a feed point in thetelevision data cable network is converted for transmission in thebackbone. In order to emit the data to the user interfaces via which auser has connected the appliance used by him, for example a personalcomputer or a television, to the television data cable network, thisdata is then once again converted from the upper cut-off area of thetransmission bandwidth. The data transfer between the user interface andthe feed point likewise takes place in the opposite direction with theaid of at least double data conversion. This makes it possible for theuser to still use his conventional cable modem via which the applianceused by him is connected to the television data cable network, eventhough the data is transmitted in a frequency range other than thatnormally used for data transfer.

This also results in the advantage that, in comparison to the known HFCtechnology, there is no need to replace the existing coaxial cables byglass-fiber cables, thus leading to considerable cost savings. The useof the upper cut-off area of the transmission bandwidth furthermoreallows the provision of adequate bandwidth for high data transmissioncapacities.

Advantageous refinements of the invention are the subject matter of thedependent claims.

The invention will be explained in more detail in the following textusing exemplary embodiments and with reference to a drawing, in which:

FIG. 1 shows a schematic illustration of a structure of a cable networkaccording to the prior art;

FIG. 2 shows a schematic illustration of a cable network with a knownHFC structure (HFC—“Hybrid Fiber Coax”) according to the prior art;

FIG. 3 shows, schematically, the use of the frequency band in atelevision data cable network according to the prior art in its originalform, and using HFC technology, for comparison;

FIG. 4 shows a schematic illustration of subdivision of a televisiondata cable network into segments;

FIGS. 5A and 5B show, schematically, the use of the frequency band in atelevision data cable network for different embodiments, with an areafor the downlink datastream and the uplink datastream in each case beingformed in the upper cut-off area of the transmission bandwidth;

FIG. 6 shows a schematic block diagram of an apparatus for processingelectronic data for bidirectional transmission of electronic data in atelevision data cable network with the frequency band being used asshown in FIG. 5A or 5B;

FIG. 7 shows a schematic block diagram of a further apparatus forprocessing electronic data for bidirectional transmission of electronicdata as shown in FIG. 6, showing an interface for local services indetail;

FIG. 8 shows a frequency plan;

FIG. 9 shows a schematic illustration of a section from the segmentedtelevision data cable network shown in FIG. 4;

FIG. 10 shows a schematic illustration of an amplifier point in thesection from the segmented television data cable network shown in FIG.9;

FIG. 11 shows a schematic illustration of a further amplifier point inthe section from the segmented television data cable network shown inFIG. 9;

FIG. 12 shows a schematic illustration of another amplifier point in thesection from the segmented television data cable network shown in FIG.9; and

FIG. 13 shows a schematic illustration of a modified amplifier point forthe further amplifier point in FIG. 11.

A method and an apparatus for bidirectional transmission of electronicdata in a television data cable network will be described in thefollowing text with reference to FIGS. 4 to 13. As can be seen from FIG.4, the television data cable network is subdivided into a number ofsegments I, II and III. Each segment may, for example, have 250 to 500user interfaces, which are normally allocated to a dwelling unit whichis connected to the television data cable network. The segments I-IIIare in the form of DOCSIS segments (DOCSIS—“Data Over Cable ServiceInterface Specification”). This is a conventional standard for thetransmission of digital data in television data cable networks. Data istransmitted within the segments I-III in accordance with the known(Euro)DOCSIS Standard. The downlink datastream (downstream) to the userinterface is normally in the form of one or two channels with a width of8 MHz. An uplink datastream (upstream) of television signals away fromthe user locations is carried out using a frequency range between 5 and28.75 MHz.

In order to carry out a bidirectional data transfer for extended mediaservices, in particular high-speed Internet data, in the transmissionband of the cable network, a backbone is provided in the exemplaryembodiment shown in FIGS. 5A and 5B, in an upper cut-off area of thetransmission bandwidth of the television data cable network, which isalso referred to in the following text as a highband, via which backbonethe data for the extended media services is transmitted to the DOCSISsegments I-III. The backbone is provided in a frequency range above 470MHz or 606 MHz (see FIGS. 5A and 5B). The backbone frequency bands arein this case adjacent to one another, with an adjacent embodiment alsobeing present when the frequency bands (uplink, downlink) are separatedin order to avoid technical problems, in particular mutual signalinterference. In this case, by way of example, it is possible to providetransmission rates of up to 1 GBit/s in each direction.

A processing device 60, as is illustrated schematically in FIG. 6, isused as the interface for processing electronic data between the DOCSISStandard and the backbone in the upper frequency range. Depending on thelocation within the segmented television data cable network, theprocessing device 60 is used for processing customer-specific data, inorder to make it possible to carry out broadband transmissions in thebackbone from a feed point to the user interfaces, or in the oppositedirection. Data conversions between the DOCSIS Standard and the uppercut-off area, in which the backbone is formed, are required for thispurpose.

The function of individual elements of the processing device 60 is shownin Table 1. TABLE 1 Ref Sym- Desig- bol nation Embodiment Function 61Tuner Highband receiver, Reception of highband downlink/uplink data fromboth directions datastream 62 Demodula- DOCSIS receiver, Demodulation ofthe tor highband downlink highband signals from datastream receiver,both directions highband uplink Demodulation of the datastream receiverDOCSIS signals from both directions 63 Central Control processorConversion of the control highband data to DOCSIS, unit and vice versa64 Modulator DOCSIS transmitter, Modulation of the highband downlinkhighband data for both datastream directions, modulation of transmitter,the DOCSIS data for both highband uplink directions datastreamtransmitter 65 Trans- Highband amplifier, Processing of the mitterdownlink and uplink modulated signals to the datastream Coaxtransmission standard 66, Splitter, Frequency splitter Separation andcombi- 67 directional nation of the fre- coupler quency ranges forremote feed, radio and television signals, highband downlink/ uplinkdatastream

Some of the functional blocks of the processing device 60 may becombined and/or may be at least duplicated. For example, the directionalcoupler 67 and the splitter 66 may be combined and may, for example, bein the form of a multistage frequency splitter (FSpW). There may be twoor more multistage frequency splitters on the output side carrying out,inter alia, the function of inputting and outputting of a remote feedvoltage. For this frequency splitter: f1<f2<f3<f4<f_(tot). f_(tot) is inthe range from 0 Hz up to and including 2.4 GHz.

The functional groups comprising the tuner 61, the demodulator 62 and/orthe modulator 64 and the transmitter 65 may be in the form of a commonblock. In any case, it should be mentioned that these functional blocksare generally at least duplicated. The central control unit 63 isassociated with functions such as a multiplexer, a demultiplexer, accesscontrol for the media, bandwidth administration, billing functions,subscriber administration and management. The functionality of thefunctional elements 61′, 62′, 64′, 65′, 66′, 67′ is comparable to thatof the functional elements 61, 62, 63, 64, 65 and 67. A B line branch70′ can be defined as the interface 70 for local services. In order toillustrate this exemplary embodiment, FIG. 7 shows one possibleconfiguration of the functional block 68. In a further embodiment (whichis not illustrated), the modulator 64′ and the demodulator 62′ may beomitted.

The plan illustrated in FIG. 8 is used for the frequency allocation in afurther exemplary embodiment. The DOCSIS uplink datastream (return path)is provided between f1 and f2, as standard. The downlink datastream istransmitted in a free television channel in the ESB (ESB=ExtendedSpecial channel Band), that is to say between f2 and f3. Depending onthe requirement for the respective transmission rate, the downlink anduplink datastream can be provided in the frequency range from f3 to f4(subdivided into 2 subareas in the frequency band).

FIG. 9 shows a schematic illustration of a section from the segmentedtelevision data cable network, in which both television data and furtherelectronic data, such as Internet data, are transmitted between a feedpoint 80 and user interfaces 81. This is done using a downlinkdatastream (DD) and an uplink datastream (DU) in accordance with theDOCSIS Standard. According to the DOCSIS Standard, conventionaltelevision data (TVDD) is transmitted as well as local data in thedownlink datastream (DD). Furthermore, electronic data is transmitteddownstream (BD) and upstream (BU) via the backbone. A processingapparatus 82 is implemented at each of two points in the sectionillustrated in FIG. 9, and these processing apparatuses 82 correspond tothe processing device 60 shown in FIG. 6. FIG. 12 shows one possibledetailed embodiment of a processing device such as this as an amplifierpoint. Further amplifier points 83 and 84 will be explained in thefollowing text, in conjunction with FIGS. 10 and 11, together with therespective functional description.

When electronic data is transmitted from the feed point 80 to the userinterfaces 81 (downlink datastream), the required electronic data is fedin at the feed point 80 digitally in a frequency range above 470 or 606MHz. The processing device 82 is used to demodulate, process andremodulate all of the transmitted data. For user interfaces which areassociated with the processing device 82, the required data istransmitted in accordance with the DOCSIS Standard in an extendedspecial channel band (ESB). For all of the other user interfaces, therequired data is once again modulated in the upper cut-off area of thetransmission band with the backbone, and is transmitted to theassociated segments. Commercially available cable modems may be used atthe user interfaces in order to demodulate the data, which is receivedin accordance with the DOCSIS Standard, for reproduction, for example bymeans of personal computers, telephones or the like.

For data transmission from the user interfaces 81 to the feed point 80(downlink datastream), the data which is fed in by the user via thecable modem at the customer end is modulated into the frequency rangebetween 5 MHz and 28.75 MHz. When the data that has been fed in in thisway reaches the first processing device, further processing is carriedout, which comprises demodulation and modulation in the upper frequencyrange with the backbone. This data is then transmitted to the feed point80 via the backbone. Any desired modulation methods which allow datacommunication at high data rates are used for data transmission in theupper frequency range above 470 or 606 MHz. For example, channels with abandwidth of 8 MHz are used in which between 38 Mbit/s and 52 Mbit/s canbe transmitted per channel, depending on the characteristics of thecable in the television data cable network. The 64-QAM or 256-QAM(QAM—“Quadrature Amplitude Modulation”) modulation method, which isknown from the DOCSIS Standard, is also used. Up to 2000 Mbit/s can betransmitted in all of the channels in the backbone. The subdivision ofthe bandwidth into a forward path and return path results in adequatedata rates in this frequency range to supply, for example, a total of5500 or 7500 users on one coaxial cable.

One or more communication processors is or are a major component of theprocessing device 60. These processors are used primarily to control adata bus, which represents the internal interface standard. Externalinterfaces are also controlled, in addition to the data bus. Theseexternal interfaces can be plugged in and can thus be interchanged. Thesimplified illustration shown in FIG. 8 illustrates three interfaces:

(a) Radio-Frequency Interface to the Output Point

-   -   This interface is designed on the basis of components based on        the DVB-C Standard (DVB—“Digital Video Broadcast”). Owing to the        capability to transport data on the basis of the DVB Standard,        both the uplink data and the downlink data to and from the        processing device are fed back to the output point by means of        this function. The amplifiers in the downlink datastream make        the downlink datastream channels available to each A amplifier        point. The assignment of downlink datastream channels to the        DOCSIS modems is likewise carried out by the processing device        60. This results in optimum flexibility with regard to capacity        assignment, since two or more DOCSIS segments can optionally use        their own downlink datastream channel or a downlink datastream        channel which is already being used by another segment. QAM 16        to QAM 256 may be used for modulation allowing a capacity of up        to 52 Mbit/s per downlink datastream channel and 8 MHz channel        bandwidth. The required backward amplifier for the upper        frequency range is a sub-octave band amplifier whose cost is        considerably less than that of the controlled downlink        datastream amplifiers, which have to amplify the entire band        from 5 to 862 MHz.        b) (Euro)DOCSIS Interface to the Cable Modems    -   The DOCSIS interface allows the use of conventional cable        modems. The electronic components which are required for DOCSIS        are commercially available, for example from manufacturers such        as Broadcom or Texas Instruments. In conventional HFC networks,        the DOCSIS modems are managed by a function in the CMTS. In the        exemplary embodiment, the management of the channels in the        DOCSIS segments (see FIG. 4) and the monitoring via the MAC        (MAC—“Medium Access”) and PHY (“Physical”) layer are carried out        by the processing device. This procedure allows each segment to        be integrated in the overall network architecture but to be        operated as an autonomous unit, thus minimizing problems        relating to the time response. For this reason, outputting to a        telecommunications network is possible at any point at which a        processing device is installed and an appropriate interface is        available. Components for the DOCSIS interface can likewise be        supplied by companies such as Broadcom or Texas Instruments.        c) Output Interface to the Backbone in the Upper Cut-Off Area of        the Transmission Bandwidth    -   The output interface to the backbone connects the coaxial        network to a telecommunications infrastructure, such as that        used by a network operator. There are a large number of        standards for this output function, which can be retrofitted        appropriately, as required. Provision is made, for example, for        the 100BaseT and STM interfaces. This allows outputting both on        copper and on an optical basis. Installation at the amplifier        point.

The implementation of the described method also requires a number offrequency splitters at the amplifier point. The frequency band issubdivided by the frequency splitters into the two areas of downlink anduplink at the A level (47-700 MHz and 750-862 MHz). The upper frequencyrange (750-862 MHz) is used for downlink datastream communicationbetween the processing devices. The lower frequency range (47-700 MHz)includes both the television channels and the downlink datastreamchannels for Internet access. The frequency splitters at the amplifierpoint on the one hand split the frequency spectrum between the uplinkdatastream, (Euro)DOCSIS and the downlink datastream, and additionallysplit the downlink spectrum into uplink and downlink channels forpassing the signals back to the output point. In the DOCSIS segments,the frequencies for the downlink datastream and the uplink datastreamare in each case determined by the processing device 60 and may beidentical for each segment, because they are not passed on to the nextsegment.

The required amplifiers for the uplink (750-862 MHz) cost considerablyless than the A amplifiers for the entire band, because: (i) this is asub-octave band and there is no need to be concerned about problems withsecond order distortion, (ii) no push-pull amplifier is required, (iii)they can be tuned more easily, and (iv) the choice of the components isconsiderably less critical.

Of the 45 free channels in the frequency spectrum from 500 to 862 MHz,10 channels are still kept free for the transmission of additionaldigital television programs. The remaining 35 channels are allocated tothe respective processing device 60 for transportation of the downlinkdatastream and of the uplink datastream. This results in a totalcapacity in the coaxial network of about 1 Gbit/s without any separateglass-fiber connection. When using the existing copper cable, thisrepresents a considerable saving rather than replacing it by glassfiber.

There are a number of possible ways to use the processing device 60 whenthe cable network is upgraded. A relatively low-cost method can beoffered by the processing device 60 and by embodiments derived from itwith a smaller range of functionalities (see the description in thefollowing text relating to FIGS. 10 to 12), which allow even relativelysmall customer groups to use the digital services of the cableoperators.

In the course of network and capacity planning, the DOCSIS segments areexpediently designed such that the maximum capacity that is available ismade use of. The DOCSIS channels are combined in the processing device60, are concentrated in a channel in the upper frequency spectrum, andare passed to the output point, specifically to the feed point or to thehandover point to the user interface. The monitoring of both the DOCSISdownlink datastreams and the uplink datastream is carried out by theprocessing device 60. Inputting of the DOCSIS signals at the B level inthe amplifier points makes it possible to continue to use thefrequencies that are used for the C levels in each segment, since theyare not passed on to the next segment. The signals which have beengathered from all of the amplifier points are emitted at the outputpoint to a telecommunications infrastructure.

When segments are connected in series, a bandwidth of about 600-700Kbit/s is available in the last clusters—comparable with a DSLconnection (calculated using a simultaneity factor of 1:6).

The frequencies which are used by the user modems in the respectivesegments of the television data cable network are loaded into theprocessing device 60 by a DOCSIS management server in the BBK or ÜBK.The processing device 60 assigns the configuration data to therespective modems in the segment, and manages the communication from themodems to the data network. Shifting the MAC/PHY layer from the CMTS tothe processing device 60 results in the various embodiments of theprocessing device 60 becoming the management unit for the DOCSIS modem,rather than the CMTS as in the case of HFC technology. In consequence,all of the processing devices 60 in the cable network are independentnodes which can take part in the communication and outputtingindependently of the control center and the CMTS. Only the centralmanagement of the frequency tables still has to be carried out in themanagement server.

One of the main differences between a glass-fiber node and theprocessing device is, in particular, the fact that the processing deviceprocesses the data and modulates it again. This processing is necessaryin order to achieve the desired efficiency in handling of the availableresources. The uplink datastream at the respective amplifier points isconcentrated in a 38 or 52 Mbit/s channel (approximately 4:1) and ispassed to the output point in the upper frequency band. The additionalconcentration results in a communication delay, which could possiblyresult in the permissible “round-trip time” from the (Euro)DOCSISStandard not being complied with. Since this time response would resultin the customer modems no longer communicating with the CMTS, the MAClayer and the PHY layer of the CMTS are integrated in the processingdevice. In addition to complying with the (Euro)DOCSIS Standard, thishas the advantage that the link between the segments can now also beprovided by a purely digital link in each case. If required, by way ofexample, one segment could be provided via a 1 Gbit/s link from the_(Arcor) since the BlueGate acts as a bridge between thetele-communications network and the cable network. As before, themanagement server functions can remain in the CMTS in order to allow theprocessing device 60 and the HFC system to be combined.

If it is intended to increase the capacity in a 450 MHz segment, thiscan be achieved by a specific replacement of the A amplifiers and of thefrequency splitters. The remote feed splitters for the return-channelare already available in the amplifier points, and are used only forinputting DOCSIS signals.

The investment required to upgrade existing cable networks is minimalwith this procedure. The described embodiment requires one processingdevice per segment, as well as an additional amplifier for the returnpath via the upper frequency spectrum. The required capacity per segmentis the governing factor for definition of the point or points at whichthe processing device or devices is or are included in the cablenetwork.

Upgrading to A Level 862 MHz Technology

The difference from the 450 MHz network is the available downlinkdatastream capacity. If the A amplifiers are upgraded to 862 MHz, thenthe frequency spectrum from about 500 MHz up to 862 MHz is available forthe downlink/uplink channels for communication from the processingdevice to the output point. This allows more user interfaces, (dwellingunits) to be connected to the cable network before having to be outputto a telecommunications network. Although the total number of possibleuser interfaces in the segment is increased, there is no need to upgradethe B and C amplifiers since the bandwidth per individual segmentremains the same. This procedure is generally worthwhile for relativelylarge networks, since up to 20 A amplifiers can be connected in series.

Upgrading on the Basis of 450 MHz Technology with InterconnectTechnology

Depending on the available telecommunications infrastructure from thecable network operator, it is possible, if required, to make use ofoutputting to third-party telecommunications lines before the signalsare passed back to the broadband cable. From the financial point ofview, this procedure may be more worthwhile than, for example, layingglass fibers. The BlueGate is for this purpose connected to thetelecommunications infrastructure only at the desired output point. Theconcentrated data in the downlink datastream and uplink datastream isemitted to an interface which is connected to the backbone in the upperfrequency range of the network. This cable network is connected to anISP (ISP—“Internet Service Provider”). This procedure allows relativelysmall segments in a cable network to be upgraded very economically. Ifthe required data volume increases subsequently, this segment can becoupled to its own infrastructure again, without any additional costs.

Capability for Combination with Conventional HFC Technology

The described method can be combined with existing HFC technologywithout any problems. This makes it possible to use HFC technology forurban network planning, where the “Rights of Way” exist for laying glassfibers. Additional glass fibers which will not be used immediately arefrequently laid for cable operator network planning. These glass fiberscan be used as a coupling for segments in which the described method canbe carried out with the aid of one or more processing devices 60.

In order to implement bidirectional data transmission, amplifier pointsare provided in the segmented cable network in accordance with theindividual requirements at the respective amplifier point. Simplifiedvariants are used in addition to the use of the processing device 60.FIGS. 10, 11 and 12 show processing devices in detail which provide thefull functionality of the processing device 60 (see FIG. 12) or only apart of it (see FIGS. 10 and 11). The following abbreviations are usedin FIGS. 10 to 12: FSpW2—new remote feed with 3 frequency bands,FSpWR—remote feed splitter with return path, RüVr—return path amplifier,A/Vr—A line amplifier, MP—measurement point, HBVr—highband amplifier,CVt—C line distributor.

In the embodiment shown in FIG. 10, only the return path is combined andamplified in the conventional frequency range from 5 to 28.75 MHz. Inthis case, it should be noted that conventional C amplifiers do not havea suitable frequency splitter. This must therefore be introduced as anadditional assembly in each case. The return paths of the C lines areemitted via new frequency splitters, and are combined with the returnpath signals from the following A line and the B lines. Afteramplification and frequency response correction, the combinedreturn-path signal is fed into the return path of the preceding A linevia the remote feed splitter (FSpWR). The functionality of the amplifierpoints in the embodiment shown in FIG. 10 corresponds to that of theamplifier points 83 in FIG. 9.

In the embodiment shown in FIG. 11, the signals in the highband (>470MHz) are also amplified in both directions, in addition to theembodiment shown in FIG. 10. There is no need for any further processingof these signals. A new remote feed splitter with an additional range isrequired (FSpw2) in order to cover the upper frequency range. The samereturn amplifiers (RüVr) can be used for combination of the return-pathsignals in the frequency range from 5 to 28.75 MHz as those in theembodiment shown in FIG. 10. In addition, a bidirectional highbandamplifier (HBVr) is required, whose directions are separated viaappropriate frequency splitters. Equalizers and attenuators must beprovided for matching to the cable connections of the incoming andoutgoing A lines. The functionality of the amplifier points in theembodiment shown in FIG. 11 corresponds to that of the amplifier points84 in FIG. 9.

The embodiment of the extended amplifier point shown in FIG. 12represents the central node for a segment to be supplied in the cablenetwork. In particular, this embodiment also provides the basicfunctionality of a DOCSIS-CMTS. The return-path signals are once againcollected in the RüVr assembly, but are not then passed to the incomingA line and, instead, are supplied to a group of DOCSIS uplink datastreamreceivers (DOCSIS demodulation). Since both the incoming A line and theoutgoing A line carry highband signals as a component of the backbone,extended remote feed splitters (FSpw2) must be used, which are knownfrom the embodiment shown in FIG. 11, must be used for connection. Theconnection for the 5 to 28.75 MHz return path to the remote feedsplitter (FSpw2) for the incoming A line is unused in this embodiment(terminating impedance). The DOCSIS uplink data is multiplexed by thecontrol processor onto the highband uplink datastream. For this purpose,all of the highband uplink datastream channels are output via frequencysplitters, and are demodulated in a group of DVB demodulators. The newlymultiplexed datastreams are supplied to a group of DVB modulators, whoseoutput signals are amplified and are fed via frequency splitters intothe incoming A line. A group of further DVB demodulators receives thedata intended for the segment to be supplied in the cable network, andthis data is converted by a group of DOCSIS transmitters (DOCSISmodulation) to the frequency range from 47 to 450 MHz that is intendedfor distribution. These channels are combined with the pure distributionsignals by means of a special combining assembly (Comb).

The embodiments illustrated in FIGS. 10 to 12 have been based on theassumption that the backbone in the upper frequency range extends onlyover one A line of the cable network. However, without any restrictions,the backbone can also be extended to B lines, and single branches arealso possible. The block diagrams of the extensions of an amplifierpoint on a B line then differ from those of the types considered so farin FIGS. 11 and 12 in that the A/BVr operates on a B line, and the BVrtogether with the associated remote feed splitters (FSpWR) is omitted(see FIG. 13). Branches are possible both in the embodiment shown inFIG. 11 and in the embodiment shown in FIG. 12. The previously unusedcoupler in the highband amplifier is used for this purpose. FIG. 13illustrates this for an embodiment which is similar to the embodimentshown in FIG. 11. In this example, the highband from the outgoing A lineis combined with the highband on one of the two outgoing B lines via thecoupler. A new frequency splitter (FSpW2) is likewise required on therelevant B line for this purpose. No provision is made for multiplebranches from the backbone from an amplifier point (Vrp) owing to thehigh coupler attenuation associated with this.

The described exemplary embodiments have been described with referenceto the DOCSIS Standard. However, the advantages of the invention arealso achieved in conjunction with other normal standards for electronicdata transmission, in particular the IEEE 802.3 Standard and the IEEE802.11 Standard.

The features of the invention which have been disclosed in the abovedescription, in the claims and in the drawing may be significant bothindividually and in any desired combination for implementation of thevarious embodiments of the invention.

1. A method for bidirectional transmission of electronic data in atelevision data cable network having segments which each comprise two ormore user interfaces, with each of the segments being connected via acable connection to a feed point for the television data cable network,and with the method comprising the following steps: a) downlinktransmission of electronic data from the feed point to at least some ofthe user interfaces of one or of all of the segments via the cableconnection, in which requested electronic data is fed into the cableconnection as digital downlink data via the feed point and istransmitted from the feed point to a processing device which isconnected downstream from the feed point in the cable connection, of afirst type; from the digital downlink data in the processing device ofthe first type, local electronic data is produced for distribution to atleast one user interface in a local segment which is coupled to theprocessing device of the first type, and electronic downlink remote datais produced for transmission in a downlink radio-frequency band in anupper cut-off area of a transmission bandwidth of the cable connection;the local electronic data is transmitted in a downlink frequency bandwithin the transmission bandwidth of the cable connection, which isformed below the downlink radio-frequency band; the electronic downlinkremote data is fed into the downlink radio-frequency band of the cableconnection by means of the processing device of the first type, and istransmitted via the cable connection to a further processing device ofthe first type; and the electronic downlink remote data is converted inthe further processing device of the first type to further localelectronic data for distribution to at least one user interface in afurther local segment which is coupled to the further processing deviceof the first type; b) uplink transmission of electronic data from atleast one of the user interfaces of one or all of the segments to thefeed point via the cable connection, in which electronically recordeduser data is fed into the cable connection via the at least one userinterface; electronic uplink remote data is produced from theelectronically recorded user data in the further processing device ofthe first type, which is connected upstream of the at least one userinterface in the cable connection; the electronic uplink remote data isfed into an uplink radio-frequency band in the upper cut-off area of thetransmission bandwidth of the cable connection by means of the furtherprocessing device of the first type, and is transmitted via the cableconnection to the processing device of the first type; and theelectronic uplink remote data is converted in the processing device ofthe first type to digital uplink data, and is transmitted via the cableconnection to the feed point.
 2. The method as claimed in claim 1,characterized in that the downlink radio-frequency band and the uplinkradio-frequency band are adjacent frequency bands.
 3. The method asclaimed in claim 1, characterized in that the upper cut-off frequency ofthe transmission bandwidth of the cable connection is used as the uppercut-off frequency for the uplink radio-frequency band.
 4. The method asclaimed in claim 1, characterized in that the downlink radio-frequencyband and the uplink radio-frequency band are formed above a frequency ofabout 470 MHz.
 5. The method as claimed in claim 1, characterized inthat the local electronic data is transmitted to the at least one userinterface in the local segment, and the further local electronic data istransmitted to the at least one user interface in the further localsegment in accordance with a DOCSIS Standard (DOCSIS—“Data Over CableService Interface Specification”), the IEEE 802.3 or the IEEE 802.11. 6.The method as claimed in claim 1, characterized in that a cable modem oran adaptor device is in each case used in the user interface.
 7. Themethod as claimed in claim 1, characterized in that the electronicdownlink remote data is amplified during the transmission in thedownlink radio-frequency band of the cable connection between theprocessing device of the first type and the further processing device ofthe first type, and/or the electronic uplink remote data is amplifiedduring the transmission in the uplink radio-frequency band of the cableconnection between the further processing device of the first type andthe processing device of the first type, by means of a processing deviceof a second type, which is connected between the processing device ofthe first type and the further processing device of the first type, withthe processing device of the second type also transmitting the localelectronic data and/or the further electronic data in the downlink anduplink directions.
 8. An apparatus for use for a method forbidirectional transmission of electronic data in a television data cablenetwork having segments which each comprise two or more user interfaces,with each of the segments being connected via a cable connection to afeed point for the television data cable network, having: b1) aprocessing module for processing digital uplink data having: outputmeans for outputting digital downlink data from the cable connection,which is fed into the cable connection via a feed point; receiving meansfor reception of the output, digital downlink data from the outputmeans; demodulation means, which are connected downstream from thereceiving means, for demodulation of the output, digital downlink data;a central control device, which has production means for production ofelectronic downlink remote data from the demodulator, output, digitaldownlink data for transmission in a downlink radio-frequency band in anupper cut-off area of a transmission bandwidth of the cable connection;modulation means for modulation of the electronic downlink remote datafor the downlink radio-frequency band; and input means for inputting themodulated electronic downlink remote data into the downlinkradio-frequency band of the cable connection; and b2) a furtherprocessing module for processing electronically recorded user data,having: further output means for outputting electronically recorded userdata from the cable connection, which is fed via at least one userinterface into the cable connection; further receiving for reception ofthe output, electronically recorded user data from the further outputmeans; further demodulation means, which are connected downstream fromthe further receiving means, for demodulation of the output and thereceived electronically recorded user data; further production means,which are formed by the central control device, for production ofelectronic uplink remote data from the demodulated, output,electronically recorded user data for transmission in an uplinkradio-frequency band in the upper cut-off area of the transmissionbandwidth of the cable connection; further modulation means formodulation of the electronic uplink remote data for the uplinkradio-frequency band; and further input means for inputting themodulated electronic uplink remote data into the uplink radiofrequencyband for the cable connection.
 9. The apparatus as claimed in claim 8,characterized by an interface device which is coupled to the centralcontrol device for transmission of local electronic data, which isproduced with the aid of the central control device, in a downlinkfrequency band of the transmission bandwidth of the cable connection,which is formed below the downlink radio-frequency band.
 10. Theapparatus as claimed in claim 8, characterized by a radio interfacedevice, which is coupled to the central control device, for transmissionof local electronic data, which is produced with the aid of the centralcontrol device, via a radio link.
 11. The apparatus as claimed in claim8, characterized by amplifi-cation means for amplification of theelectronic downlink remote data for the downlink radio-frequency band,and/or of the electronic uplink remote data for the uplinkradio-frequency band.